1. Field of the Invention
The present invention relates to an integrated type gas-insulated switching apparatus for electrical power systems, which has a container made of an insulating material and is filled with an insulating gas. More particularly, the present invention relates to an integrated type gas-insulated switching apparatus that includes a plurality of switching devices.
2. Description of the Related Art
Conventionally, various integrated type gas-insulated switching apparatuses are well known, and a typical example thereof is described in U.S. Pat. No. 5,841,087, which is shown in FIG. 18.
With the integrated type gas-insulated switching apparatus shown in FIG. 18, an isolating switch 1 is housed in a grounded metal housing 2 filled with an insulating gas, such as SF6. Stationary electrodes 3 and 4 forming switching points (contacts) are fixed to insulating spacers, and are fixed to the grounded metal housing 2 by flanges 5 and 6.
On the other hand, a stationary electrode 8 electrically connected to the grounded metal housing 2 is fixed to a flange 7. A drive shaft 10 is provided from the outside of the grounded metal housing 2 into it with the gastight of the insulating gas kept. A current terminal 11 is connected to a different device, which is not shown, to a circuit breaker, for example.
Cylindrical movable electrodes 12, 13, and 14 shown in FIG. 18 are companion to the stationary electrodes 3, 4, and 8, forming switching points (contacts) 15, 16, and 17, respectively. The movable electrodes 12, 13, and 14 are electrically conductively connected to the current terminal 11 via a metal container 18 and sliding contacts (not shown).
Busbars are connected to the stationary electrodes 3 and 4 so that the switching points 15 and 16 serve as bus selection disconnecting switches, respectively. The stationary electrode 8 is grounded, and the switching point 17 acts as a grounding switch.
A drive mechanism 19 is adapted to transmit rotational power caused from the drive shaft 10 to the movable electrodes 12, 13, and 14. The drive mechanism 19 has cams 20 and 21 connected to the movable electrodes 12 and 13 and a cam (not shown) connected to the movable electrode 15. These cams are linearly reciprocally displaced from the rotation of the drive shaft 10. The drive mechanism 19 also has levers attached to the shaft 10 so as to interact with these cams.
In the conventional integrated type gas-insulated switching apparatus described above, however, both of the switching points 15 and 16 acting as two disconnecting switches are disposed in the same metal housing 2, and the movable electrodes 12, 13, and 14 are provided directly to the common drive mechanism 19. Thus, in cases where one of the disconnecting switches (one of the switching points 15 and 16) malfunctions, it is impossible to replace the only malfunctioning switching point (i.e., disconnecting switch), because the remaining switching point (i.e., disconnecting switch) also loses its disconnecting function. It is therefore necessary to replace both switching points 15 and 16 (disconnecting switches) at the same time. This makes the replacement cost increase.
In addition, when replacing the disconnecting switches, it is necessary to disassemble the disconnecting switches on site and reassemble new disconnecting switches thereon, lengthening the time required for the replacement work.
When, on the other hand, replacing the entire apparatus including the disconnecting switches, because of transporting a large apparatus in which the disconnecting switches are assembled, the transporting work requires tremendous cost.
With the above conventional switching apparatus, the two switching points 15 and 16 acting as two disconnecting switches are provided in the same gas compartment. That is, there is no gas partition between the two switching points 15 and 16. In this state, the two switching points 15 and 16 are connected with double-busbars via no other switching points. In this configuration, in cases where, for example, one of the busbars is hit by lightning, the lightning reaches all the way into its disconnecting switch. This causes insulation breakdown in the disconnecting switch to be short-circuited to the earth, with the result that the remaining switching point connected to the remaining disconnecting switch also loses its disconnecting function. The reason is that such remaining switching point is also housed in the same gas compartment in which the short-circuiting to the earth occurred. Accordingly this makes it impossible to transmit power for all systems connected via no other switching points to the gas compartment of each of the disconnecting switches.
That is, both operations of the double-busbars stop so that it is difficult to fulfill the object of the double-busbar configuration allowing, when one of the double-busbars does not transmit power, the other thereof transmits power.